The present invention relates to an uncurling device incorporated in a facsimile transceiver or similar recording apparatus of the type using a paper roll for removing curls of the paper and, more particularly, to an uncurling device operable on the basis of the height of a curl.
It is a common practice with a facsimile transceiver, printer or similar recording apparatus to use a rolled paper. Since the rolled paper curls in the rolling direction, an uncurling device for removing the curl of the paper is incorporated in the recording apparatus. Uncurling devices of the type curling a paper with a curl in the opposite direction to the curl are disclosed in, for example, Japanese Utility Model Publication No. 33882/1988, Japanese Patent Laid-Open Publication Nos. 88270/1990, 88271/1990, and 88272/1990. The problem with this type of uncurling device is that it uncurls a paper unconditionally with no regard to the degree of a curl and, therefore, causes a paper with a small curl to curl in the opposite direction.
In the light of the above, uncurling devices capable of uncurling a paper by a variable amount matching the varying diameter of the paper roll and the weight of the paper are taught in, for example, Japanese Patent Publication No. 57019/1989, Japanese Patent Laid-Open Publication Nos. 285556/1989 and 16969/1987, and Japanese Utility Model Publication No. 119547/1986. However, since this type of uncurling device changes the uncurling amount, the structure is complicated and, since a movable uncurling section is essential, the reliability is low. During the uncurling operation, the device rubs the imaged surface of the paper to lower the image quality. Moreover, even when the roll diameter is the same, the degree of a curl depends on the paper property, print pattern, temperature and so forth, making the uncurling amount excessive or short. This is also apt to curl the paper in the opposite direction if the degree of the curl is low. In addition, this type of uncurling device is operable only with a paper in the form of a roll and not applicable to documents and cut sheets.
The uncurling device may be so constructed as to determine the degree of a curl of a paper and uncurl the paper in matching relation to the curl, as disclosed in Japanese Patent Laid-Open Publication Nos. 124463/1986 and 48343/1981 by way of example. This kind of uncurling device, however, needs a curl sensor for determining the amount of a curl, and a movable separator for changing the uncurling amount, resulting in a disproportionate cost.